Global Positioning Systems FAQs

Global Mapping Systems is proud to sponsor the development of Internet-based Frequently Asked
Question (FAQ) resources concerning the Global Positioning System. We are currently hosting the
general GPS FAQ originally written by Peter Bennett and the GPS Web Resource FAQ written by
Skeeter Abell-Smith. Both are now being maintained and updated by
karengpsy.com. Please send her corrections, updates, and
suggestions.

We regret that we are unable to answer questions on a general basis about the Global Positioning
System due to our limited staff resources although we can provide referrals to commercial consulting services. We suggest posting questions about the GPS to the newsgroup
sci.geo.satellite-nav (after reading the FAQs of course :).

The View from Space

Google's Calculator built into their seach engine
will do units conversions from meters to feet, miles to kilometers, etc. For example, just type "20 km in miles" into any Google
search field and you'll get 12.4274238 miles.

U.K.: Yeoman PLC's Navigator Pro is a
plotting table with GPS inputs that works with Admiralty charts. Quite impressive.

Waypoint Enterprises sells The Waypointer and The UTM Waypointer grid overlays
for lat/long and UTM respectively ($7.95 and $6.95) as well as a Coordinate Grid Video
by Avie Reece for $19.95. Contact them at 520-367-2600 voice or 520-367-0264 fax.

I received sample copies of the grid rulers and they seem to be well
designed and constructed. They are made out of a transparent acrylic. The lat/long grid
has rules for measuring 1:24K; 1:62.5K; 1:100K; 1:126.72K; and 1:250K. The UTM grid
has a built-in protractor for measuring degree angles an measuring ruler for 1:24000 grids. - K.

We try to keep this list of vendors as up to date as possible. Please send us any additions
or comments on any vendors (positive or negative) to
commentsgpsy.com.
We've also added our own comments on some vendors. We don't receive any "kickbacks" for our endorsements.
Since we have to buy all our own GPS units on the market ourselves, we look for the same things that
you do: a good range of GPS units, good prices, fast shipping, competent support, and a preference
to help the "little guy out."

U.S.A.: NavTech GPS -- one of the largest resellers of GPS units, books, seminars, etc.

NavTech stocks all of the major brands at reasonable prices and
have a wide range of accessories
and books on GPS and navigation technology. One important factor is
that the staff at NavTech really know their stuff -- they even offer seminars on GPS --
which makes a big difference in the level of purchasing advice and technical support
they can offer. The downside is that their prices are only moderately competitive.
Tell them that we referred you to them and ask for price matching. - K.

Many GPS manufacturers also produce GPS antennas. This section lists antenna-only
sites. I have personally evaluated both units and give them two thumbs up for their listed use:

Lowe UK -- resellers of a great, tiny, external,
active GPS antenna. This unit
is highly recommended for use with any of the small handheld GPS units, especially
the single-channels. It's a must-have for vehicle use if you have limited sky-visibility.
Its footprint is approximately 1.25" square and has an embedded magnet.
Please note that the Lowe antenna is a 5V
powered antenna and is not compatible with the 3V output of the eMap. Check with your
GPS vendor and with Lowe to make sure your antenna is voltage compatible.

MaxRAD produces a great active GPS antenna
for mobile applications called the GPSA. It's quite a bit larger than the Lowe but can be bolted
to a mounting post or rooftop (no ground plane is needed). Performance appears to
be similar to the Lowe. If I had a boat or an RV and needed a permanent antenna mount,
I would definitely consider the MaxRad GPSA. For pedestrian or automobile use, the
Lowe is smaller and lighter. The MaxRAD GPS lists for $135 and you can find a dealer
by calling MaxRad at 800-323-9122.

Variometers are flight data instruments commonly used with hang-gliders and paragliders.
They provide flight data information (altitude, lift rate, etc.) combined with moving map displays
when used with GPS units. They also provide the all-important flight data recording needed in
contests. -- tip of the hat to Alex Curlyo

APRS/HAM/Misc

Wiring your GPS/NMEA/Misc.

In general, the Global Positioning System will not suffer from either the classical Y2K
problem nor the oft-mentioned GPS-week rollover problem. Practically all
civilian and military units in circulation will not suffer from either as well.
Some of the DOD mainframe/control systems may have the Y2K problem,
however the major systems should be clear by the time the problem comes around. Despite what your
brother-in-law may have told you, planes will not come crashing to the ground and trains colliding when the digits come rolling around. Sorry to disappoint you.

However, some poorly written commercial PC or Macintosh GPS software may exhibit classical Y2K or
GPS-week rollaround problems. Of course, GPSy is not one of them. (smile)
Y2K-phobes may wish to note that NMEA-0183 suffers the classical 2-digit Y2K problem so poorly
written software may cause boats to come colliding into harbors, a'la "Speed 2: Cruise Control."
Sigourney Weaver and Demi Moore are clashing over movie rights as we speak.

This bibliographical list was originally written by Marc Brett (and taken off the
internet) with further additions by Karen Nakamura:

Copyright (C) 1997-2005 by Karen Nakamura. All rights reserved. Mention of any third party product
or reseller does not represent endorsement of or by that product or corporation.
GPSy, GPSyLink, GPSy Pro and GPSY.COM are trademarks of Karen Nakamura. All other trademarks
are the property of their respective owners.

This page was created on October 3rd, 1996 and last updated on 3 April 2005.